Found on http://www.allrecipes.com but made a few adjustments to make it SB friendly. I have not made it yet, but it got rave reviews by most of the people who wrote in. Some might not find it hearty enough for a main dish, but I think if you added some diced chicken or some type of SB friendly sausage and it could easily be hearty enough for more hefty eaters.

Directions:
1. Preheat oven to 350 degrees F (175 degrees C). Lightly grease a baking sheet.
2. Place spaghetti squash cut sides down on the prepared baking sheet, and bake 30 minutes in the preheated oven, or until a sharp knife can be inserted with only a little resistance. Remove squash from oven, and set aside to cool enough to be easily handled.
3. Meanwhile, heat oil in a skillet over medium heat. Saute onion in oil until tender. Add garlic, and saute for 2 to 3 minutes. Stir in the tomatoes, and cook only until tomatoes are warm.
4. Use a large spoon to scoop the stringy pulp from the squash, and place in a medium bowl. Toss with the sauteed vegetables, feta cheese, olives, and basil. Serve warm.